JPH0698082B2 - rice cooker - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rice cooker that is used at home and uses an induction heating coil and an ordinary heater as heat sources, and particularly relates to a heating method during heat retention.

2. Description of the Related Art A conventional general rice cooker has a structure as shown in FIG. 5, and when rice is cooked, the rice cooking heater 60 and the side heater 61 are energized, and the input power ratio is about 800W: 50W. is there. When the temperature is kept warm, the lid heater 62, the side heater 61, and the rice cooking heater 60
The ratio of its input power is about 24W: 48W: 8W. And again, the rice cooking heater 60 is a casting heater,
It is shaped so as to contact the bottom of the pan 63.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the conventional rice cooker, between the rice cooking heater 60 and the pan 63, when foreign matter is mixed, the heat of the rice cooking heater 60 is not transferred to the pan 63, and as a result, it is a casting heater. The rice cooking heater 60 has an abnormally high temperature, which is a safety issue. For this reason,
The upper limit of the input power of the rice cooking heater is about 800 W to 1000 W, which was also the cause of the limitation of shortening the rice cooking time. Therefore, in order to solve this problem, an induction heating method using an inverter, which is a heat source not in contact with the pan 63, can be considered.

Here, if an induction heating coil is placed at the bottom of the pan 63 instead of the rice cooking heater, rice can be cooked with an input power of 1000 W or more, which is the upper limit of the input power of the rice cooker of the conventional rice cooker, for example, 1200 W. For the time, the input power from the induction heating coil is OW, and the lid heater located above the pan 63
62 and the side heater 61 must be used for heat retention. However, in this case, there is a problem that the temperature of the lower portion of the pan 63 is lowered and the water vapor is condensed, and the rice in the lower portion of the pan 63 contains water, which makes the rice unfavorable.

The present invention is to solve the above-mentioned conventional problems. Instead of a rice cooking heater that is a casting heater, an induction heating coil is arranged at the bottom of a pot, and an induction heating system that uses an inverter is used to cook rice. A rice cooker with excellent heat retention characteristics that does not cause the heater to reach an abnormally high temperature, is highly safe, can shorten the time for cooking rice, and does not lower the temperature at the bottom of the pan even during heat retention. The purpose is to do.

Means for Solving the Problems In order to solve the above problems, the rice cooker of the present invention has a pot temperature detecting means for detecting the temperature of the pot, and the temperature detected by the pot temperature detecting means is higher than the heat retention temperature. A heat retention determining means for determining whether the temperature is high or low, a timer counter for measuring time, a heat retaining heater driving means for energizing the heat retaining heater located at the upper portion of the pot, and a heat retaining heater located at a lower portion of the pot than the heat retaining heater. An inverter that uses the induction heating coil as a resonance coil, an inverter driving unit that drives this inverter, and the heat retention heater driving unit and the inverter when the temperature determination unit determines that the pot temperature is higher than the temperature. An OFF signal is given to the driving means, and when it is determined that the temperature is lower than the heat retention temperature, the heat retention heater drive is performed based on the time counted by the timer counter. Means and the inverter driving means are alternately constituted by a control means for supplying an ON signal and an OFF signal.

Operation In the rice cooker configured as described above, when cooking rice, the pot and the induction heating coil that functions as the resonance coil of the inverter that is the heat source are not in contact with each other, and thus the rice cooker of the conventional method is used. The input power of 1000W or more, which is the upper limit of the input power of, can be input, and as a result, the rice cooking heater does not reach an abnormally high temperature and the rice cooking time can be shortened. In addition, since the temperature of the lower portion of the pan can be maintained at an appropriate temperature during heat retention, steam in the pan does not condense and the rice in the pan can be kept warm.

Embodiment One embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram of a rice cooker according to an embodiment of the present invention. 1 is a pot for cooking rice, 2 is a pot temperature detecting means, and this pot temperature detecting means 2 detects the temperature of the bottom of the pot 1. Reference numeral 3 denotes a heat retention determining means, which receives an output signal of the pan temperature detecting means 2 as an input and determines whether the pan temperature is higher or lower than a preset heat retaining temperature. Reference numeral 4 is a timer counter for measuring time. Reference numeral 5 is a heat retaining heater located above the pot 1, and the heat retaining heater 5 is controlled by the heat retaining heater driving means 6. 7
Is an induction heating coil located below the heat retaining heater 5 in the pan 1, and 8 is an inverter using the induction heating coil 7 as a resonance coil. Reference numeral 9 is an inverter driving means for driving the inverter 8. Reference numeral 10 is a control means. This control means 10 receives the output signals of the heat retention determination means 3 and the timer counter 4, and when the temperature of the pan 1 is higher than the heat retention temperature,
An OFF signal is given to the warming heater driving means 6 and the inverter driving means 9. On the other hand, when the temperature of the pot 1 is lower than the heat retention temperature, an ON signal is sent to the inverter driving means 9 for t1 seconds and an OFF signal is sent to the heat retention heater driving means 6 for the inverter driving means 9 during the next t2 progress. When the temperature of the pot 1 is lower than the heat retention temperature, such as an OFF signal and an ON signal to the heat retention heater driving means 6, this is repeated. Here, t1 and t2 seconds are times measured by the timer counter 4.

Here, the input power of the warming heater 5 is P1, the input voltage of the induction heating coil 7 is P2, and the ratio of the average input power of the warming heater 5 having the best warming characteristic to the average input power of the induction heating coil 7 is X: If set to Y, The values of t1 and t2 seconds are set so that

FIG. 2 shows a concrete circuit diagram of the rice cooker in one embodiment of the present invention, and FIG. 3 shows the configuration of the rice cooker. In FIGS. 2 and 3, 1 is A pot for cooking rice, and 2 is a thermistor for detecting the temperature of the pot 1.
Reference numeral 3 is a heat retention determining means, which includes a comparator 11 and a resistor 12 to
It is composed of 14 and. Then, the reference potential with respect to the heat retention temperature is input to one terminal of the comparator 11 by the resistors 13 and 14. The resistor 12, together with the thermistor 2, gives a potential with respect to the temperature of the pot 1 to the + terminal of the comparator 11. As a result, the output of the comparator 11 is a positive output when the temperature of the pot 1 is higher than the heat retention temperature, and a negative output when the temperature of the pot 1 is lower than the heat retention temperature. It can be determined whether it is high or low. 5 is a heat retention heater, and this heat retention heater 5
Is composed of a side heater 5a and a lid heater 5b, and is located above the pot 1. Reference numeral 6 denotes a warming heater driving means for energizing the warming heater 5, which is composed of resistors 15 and 16, a transistor 17, and a three-terminal thyristor 18.

Reference numeral 7 is an induction heating coil, which is located below the pot 1 from the heat insulation heater 5. Reference numeral 8 is an inverter that uses the induction heating coil 7 as a resonance coil. The inverter 8 includes an inverter control circuit 19, resistors 20, 21, and a Zener diode 2
2, switching element 23, diode 24, capacitor 25
.About.27, a coil 28, and a diode bridge 29 for AC full-wave rectification. Reference numeral 9 denotes an inverter driving means for driving the inverter 8, which is composed of resistors 30 and 31 and a transistor 32. Reference numeral 33 is a microcomputer, which receives the output signal of the heat retention determination means 3 as an input, and uses the timer counter 4 and the control means.
The output signal is provided to the inverter drive means 9 and the heat retention heater drive means 6.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. When rice cooking is completed and the warming mode is entered, in step 50, the microcomputer 30 sets the comparator
Input 11 output signals. When the temperature of the pot 1 is higher than the heat retention temperature, the output of the comparator 11 is a positive output and the process proceeds to step 51. Since the microcomputer 30 outputs a low level to the inverter drive means 9 and the heat retention heater drive means 6 to stop energizing the heater, and the inverter control circuit 19 outputs a low level to stop the drive of the inverter. The input power becomes 0. Then step 50
Then, when the temperature of the pot 1 is lower than the heat retention temperature, the comparator
The output of 11 is a negative output, and the process proceeds to step 52.

In step 52, the microcomputer 33 outputs a low level to the heat retention heater driving means 6 for t1 seconds based on the time measured by the timer counter 4, while the inverter driving means 9 is open. Is output to stop the energization of the heat retention heater 5 and drive the inverter 8.

Next, in step 53, the microcomputer 33 outputs an open state to the heat retention heater driving means 6 for t2 seconds based on the time measured by the timer counter 4, while
A low level output is output to the inverter drive means 9 to energize the heat retention heater 5 and stop the drive of the inverter 8. Then, the process returns to step 50 and the above steps are repeated. Here, steps 52 and 53 may be performed in the reverse order. In this case, the ratio of the average input power from the warming heater 5 to the average input power from the inverter 8 is a ratio having a good warming characteristic. Good.

Effects of the Invention According to the present invention, as is clear from the description of the above embodiments,
Since induction heating, which is a non-contact heat source for the pot, is used, the heater itself does not reach an abnormally high temperature even if foreign matter is mixed between the pot and the heater, unlike the conventional casting heater. , Very safe. The input power is 1000W
Although it was set as the following, rice can be cooked with more input power, so the rice cooking time can be shortened. And, during heat retention, the ratio of the input power of the upper part of the pot and the lower part of the pot can be set to the ratio with the best heat retention characteristic, so keep the temperature of the lower part of the pot where the induction heating coil is located at an appropriate temperature. Can
As a result, the steam does not condense and the rice does not contain water, and the rice can be kept warm deliciously.

[Brief description of drawings]

FIG. 1 is a block diagram of a rice cooker according to an embodiment of the present invention, FIG. 2 is a specific circuit diagram of the rice cooker, FIG. 3 is a vertical sectional view of the rice cooker, and FIG. 4 is the rice cooker. 5 is a vertical sectional view showing a conventional rice cooker. 1 ... pan, 2 ... pan temperature detection means, 3 ... heat retention determination means, 4 ... timer counter, 5 ... heat retention heater, 6 ...
Insulation heater driving means, 7 ... Induction heating coil, 8 ...
Inverter, 9 ... Inverter drive means, 10 ... Control means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiko Tanaka 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Shigeo Hamaoka, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd

Claims (1)

[Claims] 1. A pot temperature detecting means for detecting the temperature of the pot, a heat retention determining means for determining whether the temperature detected by the pot temperature detecting means is higher or lower than a heat retaining temperature, and a timer for measuring time. A counter, a warming heater located at the top of the pan, a warming heater driving means for energizing the warming heater, and an inverter having a resonance coil of an induction heating coil located at a lower portion of the pan than the warming heater, When the temperature of the pan is determined to be higher than the heat retention temperature by the inverter drive means for driving this inverter and the heat retention determination means, an OFF signal is given to the heat retention heater drive means and the inverter drive means, while When it is determined that the temperature is lower than the heat retention temperature, the heat retention heater drive means and the inverter drive means are alternately arranged based on the time measured by the timer counter. Tone signal, rice cookers, characterized by being configured by the control means for providing an off signal.